1. Field of Invention
The present invention relates to a molding method of forming a molded product from three or more semi-molded products through steps of primary molding and secondary molding, and a die assembly used for carrying out the molding method.
2. Related Art
An injection molding method is commonly known in the background art. Stationary dies and movable dies are used for carrying out the molding method. Each of these dies is provided with a predetermined-shape cavity. Accordingly, if the movable dies are opened after cooling and solidification of a molten resin injected into the cavities in the condition that the movable dies are clamped with respect to the stationary dies, a predetermined-shape molded product can be obtained. Depending on the shape of the molded product, however, it is impossible to take the molded product out even if the movable dies are opened. Therefore, when the shape of the product is so complex that the product cannot be taken out, a plurality of semi-molded products are formed separately and then bonded to one another by a method such as a vibration fusion-bonding method, a hot-plate fusion-bonding method, or the like, other than the injection molding method so that a desired product is obtained. The aforementioned complex-shape product is produced also by a die-cast molding method, a lost core method, or the like.
Although the complex-shape product can be obtained surely as described above, the background-art production method has a disadvantage. When, for example, the number of steps increases, it is general that the percentage of rejected products increases and that the efficiency of production is lowered. According to the vibration fusion-bonding method, the hot-plate fusion-bonding method, or the like, the percentage of rejected products increases more greatly and the efficiency of production is lowered more greatly because there are required two different steps of an injection molding step for obtaining semi-molded products, and a bonding step for bonding the obtained semi-molded products to one another. Further, in the vibration fusion-bonding method, not only it is impossible to obtain any complex-shape product because vibration cannot be applied to the complex-shape semi-products but also there is a problem that the product is deformed because of vibration. Furthermore, there is a defect that the product lacks reliability because fusion-bonding characteristic varies. On the other hand, according to the die-cast molding method, the lost core method, or the like, it may be possible to obtain a high-reliable product but it is unavoidable that the cost of the product increases, for example, because an expensive lost material is required.
The present invention is proposed to solve the aforementioned problem. Specifically, an object of the present invention is to provide a method of forming a complex molded product from a plurality of portions inexpensively with high quality, and a die assembly used for carrying out the method.
In order to achieve the above object, according to a first aspect of the present invention, there is provided a method of forming a molded product from three or more semi-molded products, comprising the steps of: performing primary molding in which a plurality of semi-molded products are formed in a first mold simultaneously, then a second mold is opened in a condition that the semi-molded products remain in the first mold, and the first mold is moved to collect the semi-molded products into a predetermined position; and performing secondary molding in which a molten resin is injected into contact portions of the semi-molded products which are collected and clamped to come into contact with one another, so that the plurality of semi-molded products are integrated with one another in the first mold to thereby obtain a molded product.
According to a second aspect of the present invention, the first mold is constituted by a slide mold to be slid relative to a stationary mold and slide cores to be slid in a direction different from the sliding direction of the slide mold. According to a third aspect of the present invention, a molten resin different from the resin used at the time of primary molding is injected at the time of secondary molding.
According to a fourth aspect of the present invention, there is provided a mold assembly for forming a molded product from three or more semi-molded products, comprising a slide mold provided with a predetermined number of cavities, and slide cores each provided with a predetermined number of cavities, wherein: the slide cores is configured so as to be slidable in a direction different from the sliding direction of the slide mold; and the slide mold and the slide cores are configured so as to be slidable between a position where the cavities of the slide mold are located separately from the cavities of the slide cores on one hand and another position where the cavities of the slide mold are located so as to approach the cavities of the slide cores to match therewith on the other hand.
According to a fifth aspect of the present invention, the slide cores are constituted by a pair of slide cores which are configured so as to be slidable in a direction perpendicular to the sliding direction of the slide mold.